Stepper motor sequencing fundamentals: Is the half-step sequence formed by inserting intermediate single-coil-on states between the normal full-step (two-coil-on) positions?
Digital Electronics
Digital System Projects Using HDL
Difficulty: Easy
Choose an option
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ACorrect
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BIncorrect
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COnly true for bipolar motors
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DValid only with microstepping drivers
Answer
Correct Answer: Correct
Explanation
Introduction / Context: Stepper motors can be driven in wave drive (one phase on), full-step (two phases on), or half-step modes. Half-stepping improves angular resolution and reduces resonance by interleaving states from wave and full-step sequences.
Given Data / Assumptions:
- Full-step commonly uses two phases energized for higher torque.
- Wave drive energizes a single phase at a time.
- Half-step alternates between these two patterns, doubling position resolution.
Concept / Approach: The half-step table is formed by taking the full-step sequence and inserting single-coil (wave) states between each pair of adjacent full-step states. This yields eight distinct positions per electrical cycle for a 4-phase motor instead of four, effectively halving the step angle.
Step-by-Step Solution:
Start with full-step sequence: AB, BC, CD, DA (two coils energized at each step).Insert wave states between them: A, B, C, D (single coil energized).Final half-step sequence: A → AB → B → BC → C → CD → D → DA → repeat.This inserts one-coil states between the two-coil states, creating half-steps.Verification / Alternative check:
Drive tables in motor datasheets and application notes show the mixed one/two-phase pattern for half-stepping.Why Other Options Are Wrong:
Incorrect: Ignores the standard half-step composition.Only true for bipolar motors / Valid only with microstepping drivers: Half-stepping applies to unipolar and bipolar; microstepping is finer, analog current control.Common Pitfalls:
Forgetting that torque dips during the single-coil states; some drivers boost current to compensate.Mixing up half-step with microstepping, which uses sinusoidal current control for many sub-steps.Final Answer:
Correct